Universal Material Testing Machine Research Articles

Synthesis of a novel UV-curable prepolymer 1,3-bis[(3-ethyl-3-methoxyoxetane)propyl]tetramethyldisiloxane and study on its UV-curing properties

Abstract Precursor 3-ethyl-3-hydroxymethyloxetane was synthesized with trihydroxypropane and diethyl carbonate as the main raw materials. Intermediate 3-ethyl-3-allylmethoxyoxetane was synthesized with 3-ethyl-3-hydroxymethyloxetane and allyl bromide. Prepolymer 1,3-bis[(3-ethyl-3-methoxyoxetane)propyl]tetramethyldisiloxane was synthesized with 3-ethyl-3-allylmethoxyoxetane and 1,1,3,3-tetramethyldisiloxane. Cationic photoinitiator triarylsulfonium hexafluoroantimonate of 3 wt% was added to the prepolymer, and a novel kind of photosensitive resin was prepared. Structures of the compounds obtained at individual stages of the synthesis were analyzed and characterized by FTIR and 1H-NMR. Photo-DSC analysis showed that the prepolymer had excellent photosensitivity. Thermogravimetric analysis (TG) revealed that the ultraviolet (UV)-cured samples owned excellent thermal stabilities of up to 405°C. And the mechanical properties of the UV-cured samples were tested by the universal material testing machine, giving 25.95 MPa of tensile strength, 2,935.15 MPa of elastic modulus, and 4.09% of elongation at break.

Preparation of Bis[(3-ethyl-3-methoxyoxetane)propyl]diphenylsilane and Investigation of Its Cationic UV-Curing Material Properties.

Precusor EHO(3-ethyl-3-hydroxymethyloxetane) was synthesized with diethyl carbonate and trihydroxypropane as the main raw materials. Intermediate AllyEHO(3-ethyl-3-allylmethoxyoxetane) was synthesized with 3-ethyl-3-hydroxymethyloxetane and allyl bromide as the main raw materials. Prepolymer bis[(3-ethyl-3-methoxyoxetane)propyl]diphenylsilane was synthesized with 3-ethyl-3-methoxyoxetane)propyl and diphenylsilane. Photoinitiator triarylsulfonium hexafluoroantimonate of 3% was added to the prepolymer, and a novel kind of the photosensitive resin was prepared. They were analyzed and characterized with FTIR and 1H-NMR. Photo-DSC examination revealed that the bis[(3-ethyl-3-methoxyoxetane)propyl]diphenylsilane has great photosensitivity. The thermal properties and mechanical properties of the photosensitive resin were examined by TGA and a microcomputer-controlled universal material testing machine, with thermal stabilities of up to 446 °C. The tensile strength was 75.5 MPa and the bending strength was 49.5 MPa. The light transmittance remained above 98%.

Fracture Stregnth of Endodontically Treated Teeth with Minimally Invasive Access Cavity Desgins Versus Conventional One (An In Vitro Study)

Aim: Assess the fracture strength of endodntically treated teeth with minimally invasive access cavitydesign versus conventional one.Methods: Forty four extracted molars were assigned to 4 groups. Conservative Access Cavity, Ninja AccessCavity, Truss Access Cavity, Traditional Access Cavity (n = 11/group/type). Teeth in the Traditional groupwere prepared following the principles of traditional endodontic cavities. Conservative access prepared byusing 2 periapical radiographs to determine canals location. Ninja access scans were plotted on cone beamcomputed tomographic images for localization of root canal orifices and Truss group were scanned, andmerged with cone beam computed tomography, for fabrication of an endodontic guide.The 44 specimenswere loaded to fracture in a universal material testing machine. The maximum load at which the teethfractured and fracture pattern (restorable or unrestorable) were recorded.Results: Regarding the fracture strength, results showed that there was a significant difference betweenNinja, Conservative,Truss and traditional access groups with (p < 0.001) and no significant differencebetween Conservative and Truss groups. Regarding restorability, there was no statistical difference observedbetween the four groups with (p < 0.001).Conclusion: Teeth with traditional access showed lower fracture strength than the ones prepared withConservative, Ninja and Truss.

Porous matrix nanometric scaffold repairs rabbit tibia injury by promoting bone marrow mesenchymal stem cell osteogenic differentiation and up-regulating type I and II collagen content

To explore the effect of porous matrix nanometer scaffold on Bone marrow mesenchymal stem cell osteogenic differentiation and type I and II collagen content in rabbit tibial injury. 22 rabbits, weighing 2.20–3.10 kg, were equally divided into model and treatment groups. Von Kossa was used to detect osteogenic differentiation, while Western blot detected type I and type II collagen. The bone density meter measurement software was used to assess tibial bone density. Universal material testing machine was used to detect biomechanical indicators level, while HE staining detected bone morphology. Adherent Cells growth were observed in a week; where cells clusters appeared and continued to grow 2 weeks later, and the number of osteoblasts and mineralized nodules increased significantly 3 weeks later. The collagen level in the treatment group was significantly higher than that in model group (P < 0.05). The tibia bone mineral density in model group was significantly lower at the sixth and twelfth weeks after surgery (P < 0.05). The maximum bending load and bending stiffness of model group were significantly lower than those of treatment group with higher damage degree (P < 0.05). Treatment increased the bone tissue and osteoblasts, leading to production of trabecular bone structure. No clustered regenerated bone-like tissues in model group were observed. The porous matrix nanometer scaffold can repair rabbit tibia injury possibly by promoting Bone marrow mesenchymal stem cell osteogenic differentiation and increasing type I and type II collagen level.

Research on Parameters of Wire-Filling Laser Welding and Quenching Process for Joints Microstructure and Mechanical Property of BR1500HS Steel

With the aim to investigate the effect of parameters and the quenching process on the joint microstructure and mechanical properties of hot stamping steel by laser welding, BR1500HS boron steel was welded by wire-filling laser welding with ER70-G welding wire under different parameters. The welded specimens were heated to 900 °C and held for 5 min before water quenching. A universal material test machine, optical microscope, Vickers hardness tester, scanning electron microscope, and electron backscatter diffraction (EBSD) were used to characterize. The results show that the heat input should be greater than 1040 J/cm and the optimal wire-feeding speed is between 160 cm/min and 180 cm/min. The tensile strength of the quenched joint can reach greater than 1601.9 MPa at compatible parameters. More retained austenite distributes in the fusion zone (FZ) and fine grain zone (FGZ) than the coarse grain zone (CGZ) before quenching. However, the retained austenite in FZ and heat-affected zone (HAZ) decreases clearly and distributes uniformly after quenching. The grain diameter in FZ before quenching is not uniform and there are some coarse grains with the diameter greater than 40 μm. After quenching, the grains are refined and grain diameter is more uniform in the joint. With the increase in heat input, the microhardness of FZ and HAZ before quenching decreases from 500 HV to 450 HV. However, if the wire-feeding speed increases, the microhardness of FZ and HAZ before quenching increases from 450 HV to 500 HV. After quenching, the joint microhardness of all samples is between 450 HV and 550 HV. The fracture morphology of the joint before quenching consists of a large number of dimples and little river patterns. After quenching, the fracture morphology consists of a large amount of river patterns and cleavage facets due to the generation of martensite.

Effect of Sintering Factors on Properties of Al-Rich PTFE/Al/TiH2 Active Materials.

Sintering process is an important part of the specimen preparation process, which directly affects the properties of materials. In order to obtain the best sintering control factors of Al-rich PTFE/Al/TiH2 active materials, Al-rich PTFE/Al/TiH2 active specimens with different sintering control factors were prepared using a mold pressing sintering method. A quasi-static compression experiment was carried out on a universal material testing machine, and a real stress-strain curve was obtained. The effects of sintering control factors on the properties of Al-rich PTFE/Al/TiH2 active materials were analyzed by means of mechanical parameters such as compressive strength, failure strain and toughness. SEM and XRD were used to analyze the microstructure and phase of the sintered samples. The results show that: (1) With the increase of cooling rate, the density, yield strength, strain hardening modulus, compressive strength and toughness of Al-rich Al/PTFE/TiH2 specimens decrease gradually, while the failure strain and pores of the specimens increase gradually. (2) With the increase of sintering temperature, the density, maximum true strain and toughness of the specimens first increase and then decrease, and the failure strain of the specimens gradually increases. When the sintering temperature is 360 °C, the PTFE matrix and particles inside the specimen are closely combined, a small number of particles are exposed on the PTFE matrix and there are a small number of voids. (3) With the increase of holding time at 360 °C, the strength and toughness of the material first decrease and then increase. When the holding time is 6 h, the interface between particles and matrix inside the specimen is the strongest, and the crack propagation inside the specimen is less. (4) When the sintering time increased from 1 h to 4 h at 315 °C, the compressive strength of the specimen increased by 1.62%, the toughness of the specimen decreased by 0.55% and the failure strain of the specimen decreased by 0.54%. The interface between PTFE matrix and particles is the strongest and the crack propagation is less in the specimen with a holding time of 4 h. (5) Above all, the optimum sintering parameters of Al-rich Al/PTFE/TiH2 materials are cooling rate of 25 °C/h, sintering temperature of 360 °C, holding time of 6 h and holding time of 4 h at 315 °C. (6) The reactivity of Al-rich Al/PTFE/TiH2 specimens with 10% content of TiH2 under static compression is not significantly affected by sintering parameters.

Design and parameters optimization of root cutting tool based on garlic numerical simulation model

AbstractTo obtain the best tool parameters for garlic root cutting to reduce the root cutting force and improve efficiency, a linkage occlusion‐cutting mechanism was designed for a garlic root cutting force test. The physical and mechanical properties of garlic meat and garlic skin were measured and calculated by using a universal material testing machine. A plastic follow‐up model (MAT‐3) in the LS‐DYNA material library was used as a simulated garlic material model. A three‐dimensional model of the garlic and the tool was established and imported into ANSYS/LS‐DYNA to establish a garlic root cutting simulation model. The model was used for numerical calculation and analysis. The simulation parameters were optimized according to the actual cutting force change curve, and a reliable simulation model was obtained. The error between simulated result and actual measurement was 3.5%. Based on this reliable model, the effects of tool parameters on the root cutting force were explored. The optimal blade edge angle was 11°, the optimal blade back angle was 13°, and the cutting root force was reduced by 14.94%. The reliable model and optimal tool parameters provide a reference for the design and development of garlic root cutting equipment.Practical ApplicationsGarlic is popular worldwide because of its high nutritional value and unique flavor. A reliable numerical simulation model for garlic will encourage researchers to design garlic‐processing equipment. The optimal tool parameters also provide a reference for garlic root cutting equipment.

Influence of Cold Rolling on the Recrystallization Texture and Ridging of AISI 430 Type Ferritic Stainless Steel

The effect of cold rolling on the recrystallization texture and ridging of AISI 430 type ferritic stainless steel is investigated. For comparison, the steel was cold-rolled under different reductions, two-stage rolled, and cross-rolled, respectively, and the recrystallization texture was determined by EBSD and microstructure was characterized by SEM, and the uniaxial deformation was conducted on MTS electronic universal material testing machine. The results show that in the one-stage cold rolling and annealing process, γ-fiber texture component increases with the rolling reduction, and the maximum orientation density of which appears at {334} orientation with a slight deviation from {111} . The intensity of {100} texture decreases and the other main texture components remain unchangeable. After two-stage cold rolling, the recrystallization texture returns to the γ-fiber texture that is of the feature of the ordinary bcc metals, while cross-rolling results in a recrystallization texture of mainly {100} and {111} components. It is indicated that intermediate annealing obviously improves the deviation of orientation from γ-fiber texture, which is beneficial for the steel obtaining the typical texture of bcc metals. By one-stage cold rolling and annealing process, AISI 430 type ferritic stainless steel possesses a microstructure with the texture components of {100} , {211} , {111} and {111} , with clusters of {111} , {hkl} and {hkl} grains, which deteriorates the ridging resistance, while in the two-stage rolling and annealing process, the microstructure of dispersed oriented grains shows a much better surface ridging resistance.

A Comparative Study of the Mechanical Properties of Basalt Fiber and Basalt Grille Reinforced Concrete Composites and Theoretical Prediction

ABSTRACT In this study, the chopped basalt fiber (CBF) with different content and basalt fiber grilles (BFG) with different layers were composed with concrete matrix, respectively. The compressive, splitting tensile and flexural properties of concrete composites were studied by universal material testing machine. The cracks evolution law of specimens was analyzed to reveal the reinforcement mechanism of CBF and BFG. Results showed that under the same fiber volume ratio, BFG were better than CBF to reinforce mechanical properties of concrete. The three kinds of mechanical properties of BFG reinforced concrete were improved highest by 41.46%, 28.26% and 46.13%, respectively. BFG can play a crucial role in stress transmission, bearing load and absorbing energy during the loading process of the specimens. Based on the equivalent stress rectangle theory, an analytic model to predict the ultimate flexural capacity of BFG reinforced concrete was proposed. The experimental results from the flexural test were compared with the predicted values, and a good accuracy of the analytic model was obtained.

Preparation and characterization of basalt fabrics coated with zirconia obtained by sol-gel method for textile reinforced concrete

The poor alkali resistance of basalt fabric greatly affects the mechanical properties of textile reinforced concrete. In this study, dense zirconia coating obtained by sol-gel method was coated on the basalt fabrics surface as additional sizing to improve the alkali resistance of basalt fabrics. The morphology, wettability and phase composition of the fabric surfaces was characterized by scanning electron microscopy (SEM), static water contact angle (SWCA), X-ray powder diffraction (XRD), fourier transform infrared spectra (FI-IR), X-ray photoelectron spectroscopy (XPS) and Raman. The tensile properties of various basalt fabrics immersed in alkaline solution for different time and the mechanical property of concrete composites were examined by universal material testing machine. Results showed that a protective membrane was formed on the surface of basalt fabrics to prevent the diffusion of hydroxide ions. The final strength retention ratio of BF-c-ZrO2 (Basalt fabric-coated-Zirconia) fabrics could maintain at 89.92% compared with that of pristine basalt fabrics, which reached below 40%. The compressive strength and flexural strength of BF-c-ZrO2 fabrics reinforced concrete increased by 10.15% and 19.0% compared with that of pristine basalt fabrics reinforced concrete. A theoretical model was proposed to predict the ultimate flexural bearing capacity of BF-c-ZrO2 fabric reinforced concrete based on the equivalent stress rectangle theory. The corresponding predicted value compared with experimental result indicated a good coincidence and a reasonable accuracy, which was less than 5% of their discrepancy.

A novel and efficient surgical knotting technique for high-tension closures.

BackgroundThe closure of high-tension incisions without any assistance can be difficult and challenging for surgeons. A common practice is to fix the first knot with a clamp and then tie a reverse locking knot; however, this practice has certain disadvantages. The aim of this study was to introduce a novel and efficient surgical knotting technique with various advantages.MethodsThe two knotting methods used in this study were the absorbable braided suture where the first suture was fixed with a clamp (with assistance) and the SH-9Hospital knotting technique (without assistance) applied on the smooth surface of a cylinder. Mechanical testing was performed using a universal material testing machine. The load-elongation curve and ultimate tensile load (UTL) were recorded.ResultsThe mean knotting time was 36.40±1.50 s (range, 32–41 s) and 24.80±1.16 s (range, 21–28 s) in the clamp and SH-9Hosptial groups, respectively. The mean UTL was 120.8±10.14 N (range, 81.11–136.55 N)and 126.5±6.29 N (range, 104.88–139.56 N) in the clamp and SH-9Hospital groups, respectively. The knot strength of the SH-9Hospital technique was not inferior to traditional clinical practice.ConclusionsThe SH-9Hospital knotting technique was a secure, convenient, and efficient method for high-tension closure.

Fabrication and electrochemical behavior of halloysite/ graphene-polyaniline three-dimensional hybrid aerogel loaded with iron oxide

Great progress had been made in the synthesis and application of graphene, graphene oxide (GO) aerogels, and reduced graphene oxide (rGO). However, most of the reported graphene hybrid aerogels reduced the mechanical properties of the obtained materials because of their wide pore size distribution, which limited the recycling of aerogels. Therefore, it was urgent to prepare graphene hybrid aerogels with uniform mesopores or micropores to enhance the structural stability of aerogels. Meanwhile, the mechanical and electrical properties of graphene hybrid aerogels could be further improved. In this paper, halloysite/graphene-polyaniline three-dimensional hybrid aerogel loaded with Fe3O4(HGA-PANI) was fabricated. The microstructure, mechanical properties, and electrochemical properties of HGA-PANI were characterized by scanning electron microscope (SEM), X-ray Photoelectron Spectroscopy (XPS), N2 adsorption-desorption tests, universal material testing machine, electrochemical workstation, and so on. Halloysite nanotubes (HNT) were fixed on the surface of graphene sheets or intercalated between graphene nanosheets. The three-dimensional network structure was formed, which reduced the agglomeration between graphene sheets. The hybrid of HNT and graphene sheet increased the graphene's specific surface area and constructed a three-dimensional network porous structure. Through Cyclic voltammetry (CV), Galvanostatic charge-discharge (GCD), Electrochemical impedance spectroscopy (EIS), and cycle stability tests, HGA-PANI had acceptable electrical properties, large capacitance, thin internal resistance, and amazing cyclical stability.

Fabrication and Characterization of the Core-Shell Structure of Poly(3-Hydroxybutyrate-4-Hydroxybutyrate) Nanofiber Scaffolds.

Tissue engineering scaffolds with nanofibrous structures provide positive support for cell proliferation and differentiation in biomedical fields. These scaffolds are widely used for defective tissue repair and drug delivery. However, the degradation performance and mechanical properties of scaffolds are often unsatisfactory. Here, we successfully prepared a novel poly(3-hydroxybutyrate-4-hydroxybutyrate)/polypyrrole (P34HB-PPy) core-shell nanofiber structure scaffold with electrospinning and in situ surface polymerization technology. The obtained composite scaffold showed good mechanical properties, hydrophilicity, and thermal stability based on the universal material testing machine, contact angle measuring system, thermogravimetric analyzer, and other methods. The results of the in vitro bone marrow-derived mesenchymal stem cells (BMSCs) culture showed that the P34HB-PPy composite scaffold effectively mimicked the extracellular matrix (ECM) and exhibited good cell retention and proliferative capacity. More importantly, P34HB is a controllable degradable polyester material, and its degradation product 3-hydroxybutyric acid (3-HB) is an energy metabolite that can promote cell growth and proliferation. These results strongly support the application potential of P34HB-PPy composite scaffolds in biomedical fields, such as tissue engineering and soft tissue repair.

Study on the Strength Evolution Characteristics of Cemented Tailings Backfill from the Perspective of Porosity

At present, the filling mining method is widely used. To study strength evolution laws of cemented tailings backfill (CTB) under different curing ages, in the experiment, mine tailings were used as aggregates, ordinary Portland cement (PC32.5) was used as cementing materials, and different additives (lime and fly ash) were added to make filling samples with the solids mass concentration at 74% and the cement-sand ratios 1:4, 1:6 and 1:8. Based on the nuclear magnetic resonance (NMR) technology, the porosity test of filling samples with curing ages of 3 d, 7 d and 28 d was carried out, and the uniaxial compressive strength test was carried out on the servo universal material testing machine. The relationship between the uniaxial compressive strength and porosity of backfills and the curing age in the three groups was studied, and change laws of the porosity variation and strength growth rate of backfills were analyzed. Based on the variation in porosity, the strength evolution model of the CTB under different curing ages was established, and the model was fitted and verified with test data. Results show that the uniaxial compressive strength, porosity, porosity variation, and strength growth rate of the three groups of backfills gradually increase with the increase of the curing age, the porosity of backfill basically increases with the decrease of the cement–sand ratio, and the porosity of backfill decreases with the increase of the curing age. Porosity variations and relative strength values of the three groups of backfills under different cement-sand ratios obey an exponential function, and the two have a good correlation, indicating that the established filling strength evolution model can well reflect strength evolution laws of the CTB with the change of curing age.

Investigation of Thermal Gradient Mechanical Fatigue Test Methods for Nickel-based Superalloys

Temperature gradients significantly affect the material fatigue process. A reliable and robust test procedure is needed for quantifying the effects of temperature gradients on the evolution of fatigue damage in nickel-based superalloys. The present study aims to develop a radiation heating system for universal material testing machine for simulating thermal gradient mechanical fatigue in turbines. The developed heating system mainly consists of halogen lamps, reflectors, cooling subsystems, and control units. Based on extensive experimental and computational investigations, a thermal model is developed for accurate thermo-mechanical fatigue testing under given temperature gradients in the heating system, and it is applied to variable temperature fatigue tests. The detail procedure for determining heat transfer coefficients is presented based on experimental and computational results. TGMF tests are successfully performed with the developed radiation heating system. The temperature gradients are found to reduce the TGMF life significantly in comparison to that of the TMF life. It is confirmed that the developed thermal gradient mechanical fatigue methodology can be applied to different thermo-mechanical fatigue tests with various temperature gradients.

Research on Inconel 690 material test data analysis method

The quasi-static and dynamic tensile behavior of Inconel 690 alloy are studied by universal material testing machine and split-Hopkinson bar. In this paper, seven batches of nickel-based alloy samples were tested. Through these tests, the tensile stress-strain curve and tensile stress-strain rate curve of the material and the corresponding failure parameters are obtained. The Johnson-Cook (J-C) dynamic constitutive model was used to fit the experimental data by batch and non-batch analysis methods. By comparing the fitting parameters of the two analysis methods, it is possible to obtain the fitting parameters without batches. This analysis method is more suitable for the actual situation.

Mechanical and Aging Properties of Polypropylene and Styrene-Isoprene-Styrene Composites at Low Temperature and Under Outdoor Conditions

Polypropylene (PP) and styrene-isoprene-styrene (SIS) blends with different mass fractions were prepared by twin-screw melt extrusion. PP/SIS was analyzed with differential scanning calorimetry, a universal material testing machine, capillary rheometry, X-ray diffractometry, and X-ray photoelectron spectrometry. The SIS content effect on the microstructure and properties was discussed, and the morphology and mechanical properties of outdoor-aged PP/SIS samples were studied. The SIS addition is shown to improve the PP toughness. Low-temperature tests and dynamic thermal analysis demonstrate that the low-temperature PP brittleness can be effectively enhanced by a good low-temperature SIS toughness. Indoor and outdoor aging tests revealed that the PP/SIS samples were greatly affected by the outdoor climate, but in comparison with pure PP samples, the properties of blend samples still have certain advantages offered by simple blending modification.

Effects of Modified Polytetrafluoroethylene (PTFE) on the Performance of Pan-plug Seal at Different Temperatures

Tensile and compression tests on pure PTFE, 10% carbon fiber PTFE and 20% carbon fiber PTFE were carried out on the universal material testing machine at three temperatures of 20°C, 60°C and 90°C, accepted the tensile elongation and tensile strength of this material at different temperatures. Finite element analysis is performed on pan plug seals made of three materials at different temperatures and 105 MPa. The simulation results show that when the maximum Mises stress of the outer lip of the three materials increases to a certain amount, an inflection point will appear, and the maximum Mises stress increase before the inflection point is large after the inflection point, the Mises stress increment gradually decreases. The higher the carbon fiber content, the greater the maximum Mises stress value of the lip; as the temperature increases, the seals of the three materials are less prone to tensile failure; the material with less carbon fiber content, the less stretched. When the valve stem moves up and down, the stress value of the inner lip changes more than the stress value of the outer lip; the upward stroke is conducive to the realization of the seal; the part near the end of the inner lip is more affected by the movement of the valve stem. This article provides a certain basis for the selection of pan plug seals.

Prognostic evaluation of hip joint function following capsule repair based on a threedimensional finite element analysis model

To construct a three-dimensional (3D) finite element mechanical model of total hip arthroplasty for comparison of biomechanical differences of the hip joint following capsule repair and postoperative rehabilitation. Six frozen specimens of hip joint posterior capsule ligament complex were collected in a bone-capsule-bone manner, and the load-strain curve and other mechanical properties of the specimens were tested using a universal material testing machine. Thin-section CT data of the pelvis and lower limbs obtained from a volunteer were imported into Mimics software to construct a 3D model of the hip joint. Digital models of the cup, femoral prosthesis and joint capsule were created in CATIA software and imported into Mimics to simulate total hip arthroplasty; the assembled data were imported into ABAQUS software. The properties of the capsule were set according to results of the mechanical test, anatomical studies, and constitutive equations, and the biomechanics of the anatomically repaired and conventionally repaired capsules were compared during hip flexion. The results of testing on the 6 capsule specimens showed a mean ultimate tensile strain of (39.21±5.23)% and a mean of ultimate tensile strength of 1.65±0.38 MPa. The stress-strain curve of the finite element model was consistent with the results of mechanical test on the specimens and the biochemical characteristics of the capsule. The stress was distributed evenly in the anatomically repaired capsule during hip flexion but not in the capsule repaired through the conventional approach; the tensile stress in the lower part of the conventionally repaired capsule reached the ultimate tensile stress measured on the capsule specimens at a 90° flexion. The finite element model allows dynamic, quantitative and visual assessment of stress distribution in the hip joint capsule, and compared with the conventional approach, anatomical repair can achieve better biomechanical properties of the capsule.

Mechanical response of porcine hind leg muscles under dynamic tensile loading

A modified split Hopkinson tension bar (SHTB) apparatus was used to investigate the dynamic tensile mechanical response of porcine muscles. A hollow aluminum alloy transmission bar and a semiconductor strain gauge were used to enhance the weak signal from porcine muscles. A ring-shaped copper pulse shaper was used to achieve stress equilibrium and constant approximate strain rates in the specimens. The thin muscle specimen, fixed by 3D-printed clamps, was warped around the bar ends to minimize the radial inertial effect during tensile loading. The quasi-static tests at strain rates of 0.1 s∧-1 were also conducted on a universal material testing machine to investigate the strain rate dependence. The true stress-strain curves of porcine muscle tissues along the fiber direction were determined at approximate strain rates of 800 s∧-1, 2000 s∧-1, and 3000 s∧-1. The experimental results show that the porcine muscle exhibits nonlinear, rate-sensitive, and orthotropic behavior. The Mooney–Rivlin model with two material constants was sufficient to represent the tensile response of porcine muscles at each strain rate. The rate-dependent Fields–Backofen model can describe the high strain rate response of the porcine muscles.